A MENANCE OR JUST A CRANK?

By GEORGE JOHNSON; George Johnson, an editor of The Week in Review of The New York Times, is the author of ''Architects of Fear: Conspiracy Theories and Paranoia in American Politics.''

Published: June 18, 1989

LYNDON LaROUCHE AND THE NEW AMERICAN FASCISM By Dennis King. Illustrated. 415 pp. New York: Doubleday. $19.95.

It is probably safe to assume that Lyndon Hermyle LaRouche Jr. is the only person who has ever campaigned for President with a platform that included his own version of quantum theory. The currently accepted view, you see, was foisted upon the world by that archconspirator Werner Heisenberg, whose notorious uncertainty principle - a cornerstone of modern physics - was an evil ploy to demoralize the world with the notion that at the roots of reality everything happens at random.

Or so it appears to the hyperactive band of pseudo-intellectuals that forms the inner sanctum of Mr. LaRouche's political machine. To the orderly mind of the conspiracy theorist there is no such thing as randomness. Every coincidence, every accident is meaningful. History is a war between good and evil in which everything unfolds according to plan.

For the last two decades Mr. LaRouche's followers have helped him play out his fantasy that he is the leader of a Platonic ''humanist'' elite battling a centuries-old conspiracy of oligarchs who are hellbent on subjugating the planet. Mr. LaRouche, who actually seems to believe the nonsense he spouts, hasn't had to work a day since he started running his weird show. All expenses are paid by his acolytes, who peddle tracts and magazines in airports and persuade elderly people to donate (or ''loan'') large amounts of money to fight the conspirators.

Lately it seems that the conspirators are winning. Earlier this year, Mr. LaRouche was sentenced to 15 years in prison on charges including mail fraud involving almost $300,000 in defaulted loans. Mr. LaRouche attributes his misfortunes to the conspiracy, an unlikely collection of collaborators said to have encompassed at various times Henry Kissinger, Timothy Leary, the K.G.B., the F.B.I., the Anti-Defamation League, the Rockefellers, Bertrand Russell, the British monarchy, Isaac Newton and Aristotle.

Also on the enemies list is Dennis King, the author of ''Lyndon LaRouche and the New American Fascism.'' Mr. King probably knows more about Mr. LaRouche, that master of self-delusion, than anyone, including Mr. LaRouche himself. For over a decade, Mr. King seems to have done little else but monitor Mr. LaRouche, debriefing defectors from his cult and poring over the bizarre pronouncements issued by a bewildering array of front groups - the Fusion Energy Foundation, the Schiller Institute, the National Anti-Drug Coalition, the National Caucus of Labor Committees and the National Democratic Policy Committee, which Mr. LaRouche has used to raise almost $2 million in Federal matching funds in his perennial campaigns for President.

The result of all this sleuthing has been the only consistent effort to explain what motivates this man whose half-hour campaign television spots have provided such great Saturday night entertainment. As Mr. King demonstrates, newspapers and television news programs generally consider Mr. LaRouche too loony to write about. There has long been a feeling among newspaper editors that the best way to fight political extremists is to ignore them. Mr. King shows how this hands-off policy has been partly responsible for the growing influence of Mr. LaRouche's cult.

As he documents in overwhelming detail, representatives of the various LaRouche organizations were remarkably successful in gaining audiences with members of the Reagan Administration, including a breakfast meeting with the former Interior Secretary James Watt (who was later denounced as a secret environmentalist). Mr. LaRouche and his followers have also been remarkably adept at recruiting and running candidates in local elections throughout the country. Few of these people actually have grudges against Werner Heisenberg or Aristotle, but they run on platforms crafted by Mr. LaRouche's political operatives. One of the ironies of political paranoia is how readily the conspiracy theorists seem ready to launch conspiracies of their own.

Lyndon LaRouche is descended from a long line of people who have responded to diversity by trying to stamp their false orders onto the world. In the late 18th century the Roman Catholic cleric Abbe Barruel tried to explain away the French Revolution as a conspiracy of Freemasons and a shadowy Bavarian secret society called the Order of the Illuminati.

In the United States certain members of the Federalist-Congregationalist establishment passed around books blaming a conspiracy of Freemasons, Illuminati and Jeffersonian Democrats for the country's woes. In the next century, Samuel F. B. Morse, the inventor of the telegraph, popularized his theory that the Catholic Church was plotting insurrection. Later came the vicious anti-Semitic conspiracy theories based on a faked document called the Protocols of the Elders of Zion. In the later decades of the 20th century the Trilateral Commission and secular humanists have become the focus of paranoid ravings, although there are still plenty of tracts attacking Jews and Catholics and even recycling the legend of the Bavarian Illuminati.